Radiometric dating wikipedia the encyclopedia
For example, in the The decay constant has dimensions of reciprocal seconds.In the special case in which parent and daughter atoms are present in equal quantities, the age of the specimen is the half-life of the parent isotope: The first assumption, that the amount of the daughter isotope in the original rock is known, is the weakest assumption.Radiometric dating utilizes the decay rates of certain radioactive atoms to date rocks or artifacts.Uniformitarian geologists consider this form of dating strong evidence that the Earth is billions of years old.
As time goes on, some amount of the parent decays into the radiogenic isotope of the daughter, increasing the ratio of the concentration of the radiogenic isotope to that of the daughter.
A number of radioactive isotopes are used for this purpose, and depending on the rate of decay, are used for dating different geological periods.
More slowly decaying isotopes are useful for longer periods of time, but less accurate in absolute years.
Various methods exist differing in accuracy, cost and applicable time scale.
All ordinary matter is made up of combinations of chemical elements, each with its own atomic number, indicating the number of protons in the atomic nucleus.